I was also surprised too see that they added in a the calamity aspect to the story because the one shot was interesting without it. It might have been added because the creator or an editor thought that it was needed to turn the story into a full manga series instead of just a one shot. I'm not totally put off by it though as the characters still seem like they have potential.

I guess we will have to see how it pans out in the future and if it was the right choice to add it in.